This invention relates to machines and processes for manufacturing concrete products, such as concrete pipe, manholes, catch basins, and the like. During the manufacturing process, a joint-forming ring, of cast iron or steel, is pressed into the top of the concrete pipe or manhole segment. This joint ring remains in place during the curing of the concrete in order to ensure a high quality joint. After the concrete is cured, the joint ring must be removed from the concrete product in such a way that the concrete joint of the product is not damaged.
In some operations, the joint rings are removed manually by hammering on the ring and by the use of heavy hand and power tools which involve repetitive movements by the worker that can lead to work related physical conditions. Therefore, to provide protection against cumulative trauma disorder of workers, systems have been developed to automate the joint ring removal operation. In one system, the cured concrete segment is oriented vertically and one ring at a time is pulled from the end of the pipe. As a part of the automation of the joint ring removal, the rings are gripped by appropriate grippers and a shock force is applied vertically along the axis of the pipe to free the joint ring from the product while an axially pulling force is applied. With the known prior art apparatus of this type, it is not uncommon for the concrete joint to be damaged if the pulling force is not applied uniformly to the joint ring. Even so, it is not uncommon for the shocking force, which is applied axially, to cause breakage of the concrete joint.
In another prior art system disclosed in U.S. Pat. No. 5,587,185, the joint ring removal is accomplished while the concrete pipe is positioned horizontally and the joint rings are removed simultaneously from both ends of the pipe. Although this system is utilized in high production automated systems where multiple pipes are being transported along a horizontal conveyor, there is a need for a joint ring removal apparatus and method in production facilities where the concrete pipes are stored vertically for curing and are individually handled using automated robotics. The method and apparatus of the invention will satisfy this need by providing an apparatus and method for removing a joint ring from a cured finished product in a manner that will greatly minimize, if not eliminate, damage to the concrete joint.
The method and apparatus of the invention provides a joint ring removal system in which a vertically oriented concrete product containing a joint ring is gripped to hold the product stationary while the joint ring pulling force is applied, and then a shocking force is applied laterally to the joint ring. The amount of pulling force applied to the joint ring is less than that required to separate the joint ring from the concrete while the shocking force is applied in a direction transverse to the pulling force so that no harmful tensile shocking forces are transmitted to the concrete joint. The pulling force on the joint ring is variably applied and timed with the shocking force. The pulling force is applied at multiple locations to the joint ring, and the force at each location is monitored so that the pulling force is applied equally at all locations.
The advantages and features of the method and apparatus of the invention will become more evident from the detailed description of the preferred embodiment set forth hereinafter.